| Primary Identifier | IPR000032 | Type | Domain |
| Short Name | HPr-like |
| description | This entry represents a structural domain found in both the histidine-containing phosphocarrier protein HPr, as well as its structural homologues, which includes the catabolite repression protein Crh found in Bacillus subtilis [, ]. This domain has a alpha+beta structure found in two layers with an overall architecture of an open faced β-sandwich in which a β-sheet is packed against three α-helices. The histidine-containing phosphocarrier protein (HPr) is a central component of the phosphoenolpyruvate-dependent sugar phosphotransferase system (PTS), which transfers metabolic carbohydrates across the cell membrane in many bacterial species [, ]. PTS catalyses the phosphorylation of incoming sugar substrates concomitant with their translocation across the cell membrane. The general mechanism of the PTS is as follows: a phosphoryl group from phosphoenolpyruvate (PEP) is transferred to Enzyme I (EI) of the PTS, which in turn transfers it to the phosphoryl carrier protein (HPr) [, ]. Phospho-HPr then transfers the phosphoryl group to a sugar-specific permease complex (enzymes EII/EIII). HPr [, ]is a small cytoplasmic protein of 70 to 90 amino acid residues. In some bacteria, HPr is a domain in a larger protein that includes a EIII(Fru) (IIA) domain and in some cases also the EI domain. A conserved histidine in the N-terminal section of HPr serves as an acceptor for the phosphoryl group of EI. In the central part of HPr, there is a conserved serine which (in Gram-positive bacteria only) is phosphorylated by an ATP-dependent protein kinase; a process which probably play a regulatory role in sugar transport. Regulatory phosphorylation at the conserved Ser residue does not appear to induce large structural changes to the HPr domain, in particular in the region of the active site [, ]. |
